Paraffin control device



July 4, 1967 BE. ROACH PARAFFIN CONTROL DEVICE 4 Sheets-Sheet l v .55 E i Filed June 24 1964 frJ/r/ne f. Roar/2 INVENTOR.

A7'7'0l?/\/ V July 4, 1967 E. E. ROACH PARAF'FIN CONTROL DEVICE 4 Sheets-Sheet 2 Filed June 24, 1964 f/J one R0006 IN VEN TOR.

ATTOR/VE y July 4, 1967 E. E. RoAcH PARAFFIN CONTROL DEVICE 4 Sheets-Sheet 5 Filed June 24, 1964 AFTER/V5) United States Patent Ofiice 3-,329,2 ll Patented July 4, 1967 3,329,211 lPAlRAFFIN CGNTROL DEVICE Erskine E. Roach, Houston, Tex, assignor to Harold Brown Company, a corporation of Texas Filed June 24, 1964, Ser. No. 377,565 8 Claims. (Cl. 166170) This invention relates to paraffin control devices for Wells and more particularly for flowing oil wells.

Many crude petroleum oils carry varying quantities of paraflin which, due to changing well temperature and pressure conditions during production, tends to precipitate from the oil and deposit on the walls of the production pipe or tubing.

When initially deposited the paraflin is relatively soft and may be easily removed by suitable scraping or wiping means. If thus properly removed, the paraflin will not redeposit but will be suspended in the crude oil and be produced with it. However, if the paraffin remains on the pipe walls for several days, for example, it will harden, become sticky, and, in general, be much more diflicult to remove. Also, continued accumulation without control will completely plug off the inside of the production tubing, requiring costly removal measures in order to clear the tubing.

There are a number of means currently employed for controlling or preventing paraflin deposits. These methods are (l) Injecting paraflin solvent; (2) down-the-hole heaters on the tubing string; (3) plunger or scrapers driven by the flow in the tubing; and (4) mechanical removal by wire-line tools.

All of the above work to varying degrees of success and the most positive means is by mechanical removal with wire-line tools. Therefore, this method is most commonly used, even though it is the most expensive control means.

Paraflin plungers or scrapers, commonly called rabdiflicult to apply successfully. It must be batch pumped down the tubing or injected through a parallel string of tubing. This method is not normally used down the tubing, but is sometimes used to control paraflin in the flow line.

Down-the-hole heaters are not only expensive to install but require large amounts of power for eifective control.

Paraffin plungers or scrapers, commonly called rabbits, of various kinds have been used with varying degrees of success. These rabbits usually require that the Well be shut-in while the plunger is falling. Also, they require a moderately high flowing rate of the well fluids in order to make the plunger return to the surface. There are not many flowing wells in which the plungers or rabbits are run satisfactorily.

The mechanical removal of the paraflin deposit by wire-linecarried cutters is by far the most successful and positive means of controlling paraffin deposits. This is done manually, using portable wire-line units which move from well to well on routine schedules. Frequent cutting of paraflin is required in many flowing wells, but this method is quite expensive and accounts for a large fraction of the total operating cost of many flowing wells It is, therefore, a primary object of this invention to provide paraflin control devices which will obviate the disadvantages described above of the more conventional systems.

It is an important object of the present invention to provide a paraffin control device of the plunger or rabbit type which is automatic in operation and which does not require a high flow rate in the well to cause the device to surface.

It is a further object of this invention to provide a paraffin control device employing a well plunger of the free-piston type which will fall to the low point in its travel by gravity propulsion through the well fluids in the tubing and which carries a buoyancy chamber means which is operable by entrapment of gasiform fluids from the well fluid to increase the effective buoyancy of the plunger in the well fluids sufliciently to cause the plunger to rise to the surface.

Yet another object is the provision of a paraffin control device which employs a well plunger of the free-piston type carrying scraper or wiper elements for wiping engagement with the wall of the tubing and which includes means for increasing the eifective buoyancy of the plunger in the well fluids present in the well tubing, the buoyancyincreasing means comprising an elongate chamber having longitudinally spaced openings adapted to initially allow passage of well fluids therethrough so as to allow the device to fall by gravity to its low point and means carried by the plunger closing-oil the upper openings in the bouyancy chamber to cause the entrapment of gasiform fluids from the well fluids in the chamber to thereby increase its effective buoyancy.

A more specific object is to provide a two-part structure comprising a plunger of the free-piston type and an elongate tubular housing separably connectible to the lower end of the plunger, the lower end of the latter and the upper end of the housing defining valve elements cooperable when the plunger and housing are connected to close off the upper end of the housing for entrapment of gasiform fluid from the well fluids.

An additional object is the provision of a paraffin control device employing a free-piston type plunger and an elongate tubular housing defining a buoyancy chamber having upper and lower longitudinally spaced openings for passage of well fluids therethrough, the housing being separably connected to the plunger and adapted to fall to the low point in the well in advance of the plunger and to be telescopically engaged by the latter to close off the upper openings in the chamber to permit entrapment therein of gasiform fluids from the well fluids, whereby to increase the effective buoyancy of the device in the Well fluids sufficiently to cause the device to raise automatically to the surface.

Still another object is the provision of a paraffin control device employing a plunger of the free-piston type having an elongate buoyancy chamber incorporated therein, said,

chamber having longitudinally spaced upper and lower openings therein for the passage of well fluids therethrough and valve means mounted on the body operable to open and close the upper openings upon attainment by the plunger of the upper and lower terminals, respectively, of its movement in a well production pipe.

Other and more specific objects and advantages of this invention will become more readily apparent from the following detailed description when read in conjunction with the accompanying drawing which illustrates several useful embodiments in accordance with this invention.

In the drawings:

FIG. 1 is a longitudinal sectional view of a two-part device in accordance with one embodiment of this invention, showing the parts in connected relation;

FIG. 2 is a fragmentary view of the device of FIG. 1, showing the parts in separated relation;

FIGS. 3 to 6, inclusive, are generally diagrammatic, partly sectional views illustrating the surface control equipment employed in operation of the device of FIGS. 1 and in a well, and the positions of the parts during several stages of operation;

FIG. 7 is a longitudinal sectional view of another embodiment in accordance with the invention, showing the parts in the positions occupied during non-buoyant condition of the device; and

FIG. 8 is a view similar to FIG. 7, showing the parts in the positions occupied during buoyant condition of the device.

Referring first to the embodiment illustrated in FIGS. 1 and 2, the rabbit is a two-part structure comprising a plunger section, designated generally by the numeral 1, and a buoyancy section, designated generally by the numeral 2. Plunger section 1 may, in its general construction, correspond to any of the well known plungers of the free-piston type commonly employed for pumping oil wells. Examples of plungers of this general type are illustrated in, among others, U.S. Patents Nos. 2,878,754, 3,020,852, 3,012,513. As herein illustrated, plunger section 1 comprises a generally tubular body 3 having an axial bore 4 extending entirely therethrough. A nose portion 5 having a conically tapered tip 6 is threadedly connected to the lower end of body 3 and has a counter-bore 7 co-axially communicating with bore 4 at one end and at the other end with a smaller diameter axial passage 8 extending to the outer end of tip 6. A plurality of generally radial ports 9 provide communication between counter-bore 7 and the exterior of tip 6 at points spaced rearwardly from the outer end of the tip. The upper end of nose portion 5 forms an upwardly facing annular shoulder 10 and the upper portion of body 3 is provided with an annular enlargement 11 defining a downwardly facing annular shoulder 12 longitudinally spaced from shoulder 10. A plurality of wiper rings 13 are mounted in a loose arrangement about body 3 between shoulders 10 and 11. These rings 13 may be in the form and arrangement described in greater detail in U.S. Patents 2,878,754 and 3,020,852 for effecting both wiping and sealing engagement with the well pipe or tubing in which the device is run. Various other forms of wiping and sealing structures may be employed on the plunger section of the device, the particular form and arrangement of these elements not being a part of this invention, it being only necessary to provide a construction which will serve to yieldably wipe or scrape the wall of the pipe as the device travels through the pipe. While it is desirable that the wiping elements function also as a seal, this is not essential in all cases. Body 3 may include an upward extension 14 provided with a fishing head 15 for connection of a conventional fishing tool in the event the device fails to return to the surface during its operation.

Buoyancy section 2 is adapted to be separably connected to plunger section 1 and comprises a tubular housing 18 defining a chamber 19 in the interior thereof and terminates at its lower end in a generally frusto-conical nose portion 20 having an end wall 21 closing the lower end thereof and provided withlaterally extending ports 22 to provide communication between the interior of chamber 19 and the exterior of the buoyancy section. The upper end of housing 18 is provided with a closure member 23 of re-entrant frusto-conical shape complementary, in general, to the shape of tip 6 of the plunger section and adapted to telescopically receive the same in closefitting relation. The inner end of closure member 23 is closed by means of an end wall 24 and the side wall thereof is provided with lateral ports 25 positioned at points intermediate end wall 24 and the opposite end of closure member 23. The exterior of tip 6 carries a pair of longitudinally spaced seal elements 2626 positioned thereon below ports 9 and arranged to seal between tip 6 and the inner wall of closure member 13 above and below ports 25 when tip 6 is fully inserted in closure member 23, as illustrated in FIG. 1.

By employing tip 6 and closure member 23, constructed as described, it will be seen that tip 6 serves as a valve means operable to close ports 25, for purposes to be described hereinafter.

Generally stated, operation of this embodiment of the invention is as follows:

Buoyancy section 2 will be separated from plunger section 1, as seen in FIG. 2, and will be caused to fall by gravity through the fluid in a well pipe or tubing, through which well fluids are allowing. In their separated relation, lower ports 22 and upper ports 25 will allow free passage of the well fluids through chamber 19 and will, therefrom, permit free fall of buoyancy section 2 through the well fluids to the lower terminus of its movement in the well pipe, which will usually be by engagement with a conventional tubing stop, indicated at S (FIGS. 3 to 6), positioned in the production tubing T. The buoyancy section will then be followed by the plunger section which, since ports 9 and passage 8 are open, as well as the upper end of bore 4, and will also fall by gravity through the well fluids in the tubing until tip 6 enters closure 23 and closes off fluid passage through upper ports 25. When this occurs, gas or other gasiform fluids normally carried in the well fluids, such as oil, will rise inside chamber 19 to the top there-of and being trapped in the chamber will displace the liquid in chamber 19 out of lower ports 22 until the effective buoyancy of the combined structure has increased to a point which will tend to cause the device to float upwardly through the well fluids to the surface. It is usually necessary only that the buoyancy be increased to a point such that the buoyancy, either alone, or in combination with any differential fluid pressure across the plunger section, will cause the device to move upwardly through the well fluid to the surface. Since the rabbit is used in flowing oil wells, any sealing action of the wiping elements will function to develop a differential pressure across the plunger section which will aid the upward movement of the rabbit.

As the device travels upwardly, the elements 13 will wipe the wall of the well pipe or tubing, removing the parafiin and thereby cleaning the wall.

The dimensions of buoyancy section 2 may be varied in accordance with the weight of the device and the pressure and flow conditions in the well to provide the re quired buoyancy for accomplishing the purposes of this invention.

Suitable means may be provided at the surface to separate the two sections of the device and to allow them to return sequentially by gravity to the bottom to be re-engaged and begin another cycle.

FIGS. 3 to 6 illustrate apparatus for rendering automatic the return of the rabbit to the bottom of the well on a predetermined timing cycle. Tubing T is shown disposed inside a conventional well casing C through which it extends from a suitable point in the well to the surface, passing through a casinghead H and controlled by a master valve M. A tubular lubricator L is mounted on the master valve and has a co-axial extension E for enclosing some of the equipment. Lubricator L has a side outlet conduit 0 connected thereto for discharge of well fluids flowing to the surface. Mounted on lubricator L between master valve M and outlet conduit 0 is a catcher device D of generally well known construction, adapted to catch plunger section 1 when it rises to the surface and enters the lubricator. Catcher device D includes an internal trigger element 30, depression of which by arrival of the plunger, opens communication between a suitable source of pilot gas supply from a line 31 to a line 32 leading to a three-way pilot valve 33 having an inlet port 34, an outlet port 35, and a vent port 36 controlled by a valve 37 having a stem 38 secured to a pivoted weight bar 39 arranged in a generally conventional manner, to be moved by a timing wheel 40. Discharge port 35 communicates via a line 41 with a cylinder 42 in catcher device D in which is mounted a catcher piston 43 adapted to thrust against the plunger upon its arrival in response to the pressure of gas supplied from pilot valve 33. A branch pipe 44 connects to line 41 and leads to the piston chamber of a three-way spool valve 45. The latter includes a sliding spool 46 movable between positions communicating a vent port 47 and a pressure gas supply port 48 alternately with a discharge port 49 which is in communication, via a line 50, with the upper end of a cylinder 51 provided in the upper end of extension E and housing a piston 52. The latter is mounted on the upper end of a rod 53 which extends downwardly through a cylinder head 54 and through a bumper bolck 55 resiliently biased downwardly by a spring 56 mounted in compression between cylinder head 54 and bumper block 55. A separate pressure gas supply source is connected with port 48 through a line 57.

FIG. 3 shows the position of the parts awaiting arrival of the rabbit shown moving upwardly through tubing T under the influence of its own buoyancy and the pressure forces of the flowing well fluids.

In FIG. 4, arrival of the plunger in lubricator L actuates the gas supply control in the catcher device and directs gas through inlet and outlet ports 34 and 35 of the pilot valve via line 41 to cylinder 42. ofthe catcher, urging piston 43 inwardly so as to grip plunger section 1 strongly and retain it in the lubricator. Entrance of the plunger into the lubricator will cause the lower end of the rod 53 to enter bore 4 of the plunger section, as illustrated particularly in FIGS. 1 and 4. At the same time, gas discharging from port 35 of the pilot valve through line 41 will flow through line 44 into the piston chamber of spool valve 45 moving valve 46 upwardly to the position shown in FIG. 5, wherein discharge port 49 is put into communication with supply port 48, allowing pressure gas to flow through line 50 into the top of cylinder 51, forcing piston 52 downwardly and thrusting rod 53 through the entire length of plunger section 1 urging its lower end against end wall 24, thereby forcibly pushing buoyancy section 2 off of tip 6 of the plunger section and opening upper ports 25 in the buoyancy section. This will release any gas trapped in the buoyancy section and allow free flow of well fluids therethrough. Thereupon, the buoyancy section, being freed from the plunger section, will fall by gravity through the well fluids in tubing T back to its lower terminus, namely, tubing stop S, as seen in FIG. 5. This condition prevails until timing wheel 40 has rotated to a position placing a notch 60, or similar actuating element, arranged at a previously selected location on the timing wheel, in position to cause weight bar 39 to swing downwardly, moving pilot valve 37 to the position closing port 34 and opening vent port 36, thereby cutting off of gas to catcher piston 43. The latter, being relieved of the pressure of the gas, will be forced outwardly by the weight of plunger section 1 which will then be freed to fall downwardly by its own weight through the fluid in tubing T and follow buoyancy section 2 downwardly until it reengages with the latter to initiate the return movement of the rabbit. Venting of the supply gas through vent 36 will likewise vent the gas pressure acting on spool valve 46 and allow the latter to move back to its original position, cutting off the independent pressure gas supply through inlet port 48 and again placing discharge port 49 in communication with vent port 45, thereby relieving pressure from the top of cylinder 51 and allowing piston 52 to be returned to its retracted position under the pressure of well fluids in the lubricator.

By selection of a suitable timing interval in relation to the fluid flow and pressure conditions in the well, the amount of gas in the well fluids and other readily determinable factors, the rabbit may be caused to repeat its upward and downward movement on any suitable cycle. It will be seen also that the rabbit may function both as a free-piston type pump and as a parafiin scraper in wells in which the flow rate will ordinarily be too low for use of more conventional free piston plungers, the important improvement provided by the present invention being the addition of the buoyancy section to an otherwise generally conventional free piston type plunger.

FIGS. 7 and 8 illustrate a modification in which the buoyancy chamber is incorporated entirely within the plunger body. Operation of the device may also be somewhat simplified in those wells where this particular embodiment may be effectively employed.

As illustrated in FIGS. 7 and 8, the modified device comprises a plunger section 1a which includes a tubular body 3a which is extended in length to incorporate therein a buoyancy section 2a of the required volumetric dimensions. The latter includes a tubular housing 18a, to the lower end of which is connected a bottom head 65 having a through bore 66 communicating with bore 19a of housing 18a and bore 4a of the plunger section. The upper end of the latter defines an upper valve housing 67 having a bore 68 terminating at its upper end in a conically tapered end wall 69 which merges with an upwardly extending fishing neck 14a which carries the fishing head 15a. Wall 69 has a bevelled inner surface defining a valve seat 70 which is pierced by upper ports 71 providing communication between the interior of valve housing 67 and the exterior of the device. Plunger body 3:: carries wiper rings 13a, like those in the previously described embodiment.

A valve 72 is slidably mounted in bore 68 of valve housing 67 being resiliently supported on the upper end of a valve. rod 73 by means of a compression spring 74, one end of which is seated in a socket 75 in the valve and the other end on a shoulder 76 on the'valve rod, the spring serving to bias valve 72 toward seat 70. Valve 72 has a bevelled upper end face 77 in which is seated an annular packing 78 adapted to engage seat 70 interiorly of ports 71 and thereby seal off the ports from the interior of the plunger when the valve is moved to its uppermost position illustrated in FIG. 8. Valve 72 carries an axial upward extension 79 which has a length such as to project a short distance from the upper end of fishing neck 14a when the valve is in sealing engagement with seat 70.

A striker block 80 is slidably mounted in bore 66 of bottom head 65 and is resiliently biased in the downward direction from the lower end of valve rod 73 by means of a compression spring 81, one end of which is seated in a socket 82 in block 80 and the other end on a shoulder 83 provided on the lower end of valve rod 73. An internal shoulder 84 in bore 66 limits upward movement of striker block 80. The lower end of the latter carries an axial downward extension forming a striker pin 85 which extends through an axial opening 86 in the lower end of the bottom head. The length of pin 85 is made such as to project a short distance below the lower end of bottom head 65 when the lower end of striker block 80 is substantially in engagement with a lower internal shoulder 87 in the bottom head, as seen in FIG. 7. Strike pin 85 is provided in its exterior surface with upper and lower longitudinally spaced shallow grooves 88 and 89, respectively, adapted to be latchingly engaged by a ball detent mounted in the wall of opening 86. In one position, FIG. 7, detent 90 engages upper groove 88 to latch the striker pin in its projected position. In the second position, seen in FIG. 8, detent 90 is engaged in lower groove 89 in which position striker pin 85 is held in its retracted position. Lateral ports 91 provide communication between the interior of buoyancy chamber 18a near its lower end and the exterior of the device.

In operation, the last-described embodiment is inserted in a well tubing with the parts in the positions illustrated in FIG. 7, in which extension 79 has been forced inwardly by engagement at the upper terminus of its movement to the surface with a suitable stop such as bumper block 55. This moves valve 72 away from seat 70, opening ports 71. The downward force thus applied to valve 72 will be transmitted through compression spring 74 to valve rod 73 and thence through lower compression spring 81 to striker block 80, forcing the latter downwardly to the position at which detent 90 is engaged in upper latching groove 88, thereby holding striker pin 85 in its projected position. With ports 71 now open, as are lower ports 91, the pressure inside and outside the device will be equalized and fluid is free to flow through the interior of the device which will now fall by gravity through the fluid in the tubing until the projecting end of striker pin 85 strikes tubing stop S (FIG. 8). The force of this impact will force block 80 upwardly out of locking engagement of detent 90 in upper latching groove 89 and move lower latching groove 88 into latching engagement with the detent. The upward movement of block 80 will compress lower spring 81 and the resultant force will be transmitted through valve rod 73 and upper spring 74 to valve 72 which will be moved to its sealing position on seat 70 closing off upper ports 71 (FIG. 8).

As in the previously described embodiment, closing of the upper ports will trap gas evolving from the well fluids in the body of the device and displace liquids out of lower ports 91 until the effective buoyancy of the device has increased sufficiently to cause the device to rise to the surface, wiping paraflin from the tubing wall as the device travels upwardly therethrough.

With this embodiment, it will be evident that push rod 53 and the portions of the surface control equipment required for operating this element may be eliminated, the catching and automatic release of the plunger on a timed cycle being otherwise the same as in the earlier described embodiment.

The buoyancy chamber arrangement herein described may be employed in conjunction with paraffin control means other than wiper elements mounted on a plunger of the free-piston type. For example, a chemical injector device of the character illustrated and described in my US. Patent No. 2,852,080 may be employed for controlling the paraflin deposit and the buoyancy chamber may be added to the structure to provide the automatic operation as herein described.

It will be understood that changes and modifications may be made in the details of the illustrative embodiment within the scope of the appended claims but Without departing from the spirit of this invention.

What I claim and desire to secure by Letters Patent is:

1. A paraffin control device for well pipes, comprising, a generally tubular body insertable in a well pipe for reciprocating travel therein, said body being constructed to travel by gravity in the downward direction, and to travel in the upward direction in response to differential pressure forces across said body from well fluids in said pipe, wiper elements constructed and arranged about the exterior of the body for slidable wiping and sealing engagement with the wall of the well pipe, and an elongate housing defining a buoyancy chamber carried by the body, said housing having means operable upon attainment by the body of the terminus of its downward movement to entrap gaseous fluid in said chamber from the well fluids whereby to increase the effective buoyancy of said body in the well fluids, said housing being separable from said body for insertion in said well pipe in advance of said body for said movement in the downward direction.

2. A paraffin control device for well pipes, comprising, in combination with a well plunger of the free-piston type including a generally tubular body insertable in a well pipe for longitudinal movement therein and wiper elements mounted about the body for wiping engagement with the wall of the well pipe, means for increasing the effective buoyancy of said body in well fluids present in said pipe comprising an elongate hollow housing carried by the body and defining a buoyancy chamber, said housing having longitudinally spaced upper and lower openings therein for passage of well fluids through said chamber, and means carried by said body operable to close said upper openings without closing said lower openings when said plunger is at the terminus of its downward travel in said well pipe, whereby to trap gasiform fluid evolving from said well fluids in said chamber.

3. A paraflin control device for well pipes, comprising, in combination with a well plunger of the free-piston type including a generally tubular body insertable in a well pipe for longitudinal movement therein and wiper elements constructed and arranged about the body for wiping and sealing engagement with the wall of the well pipe, means for increasing the effective buoyancy of said body in well fluids present in said pipe comprising an elongate hollow housing carried by the body below said wiper elements and defining a buoyancy chamber, said housing having longitudinally spaced upper and lower openings therein for passage of well fluids through said chamber, and valve means carried by said body operable to close said upper openings when said plunger is at the terminus of its downward travel in said well pipe, whereby to trap gasiform fluid evolving from said well fluids in said chamber.

4. A paraflin control device for well pipes, comprising, in combination with a well plunger of the free-piston type including a generally tubular body insertable in a well pipe for longitudinal movement therein and wiper elements constructed and arranged about the body for wiping and sealing engagement with the wall of the well pipe, means for increasing the effective buoyancy of said body in well fluids present in said pipe comprising an elongate hollow housing separably connectible to the body below said wiper elements and defining a buoyancy chamber, said housing having longitudinally spaced upper and lower openings therein for passage of well fluids through said chamber, and closure means carried by said body insertable into said housing operable to close said upper openings when said housing and said plunger successively attain the terminus of their downward travel in said well pipe, whereby to trap gasiform fluid evolving from said well fluids in said chamber.

5. A paraflin control device for well pipes, comprising, in combination with a well plunger of the free-piston type including a generally tubular body insertable in a well pipe for longitudinal movement therein and wiper elements constructed and arranged about the body for wiping and sealing engagement with the wall of the well pipe, said movement in the downward direction being gravity-propelled and in the upward direction being in response to differential pressure forced across said body from well fluids in said pipe, means for increasing the effective buoyancy of said body in said well fluids comprising, an elongate hollow housing defining a :buoyancy chamber separately insertable in the well pipe in advance of said plunger, said housing having longitudinally spaced upper and lower openings therein for passage of well fluids through said chamber, and closure means carried by said body insertable into said housing and operable to close said upper openings when said plunger engages said housing at the terminus of their downward travel in said well pipe.

6. In a well plunger of the free-piston type, including a generally tubular body insertable in a well pipe for longitudinal movement therein, and wiper elements mounted about the body for slidable wiping engagement with the wall of the well pipe, means for increasing the effective buoyancy of said body in well fluids present in said pipe comprising an elongate hollow housing carried by the body and defining a buoyancy chamber, said housing having longitudinally spaced upper and lower openings therein for passage of well fluids through said chamber, and means carried by said body operable to close said upper openings without closing said lower openings when said plunger is at a low point in its travel in said well pipe whereby to trap gasiform fluid evolved :from said well fluids in said chamber.

7. A paraffin control system for well pipes, comprising, in combination, a generally tubular body insertable in a well pipe for longitudinal movement therein, wiper elements constructed and arranged about the body for slidable wiping and sealing engagement with the wall of the well pipe, said movement in the downward direction being gravity-propelled and in the upward direction in response to diflerential pressure forces across said body from well fluids in said pipe, means for increasing the efiective buoyancy of said body in said well fluids comprising an elongate hollow housing carried by the body and defining a buoyancy chamber, said housing having longitudinally spaced upper and lower openings therein for passage of well fluids through said chamber, valve means carried by said body operable to close said upper openings without closing said lower openings when said body is at the lower terminus of its travel in said well pipe, and means at the surface operable by arrival of said body at the terminus of its upward travel to re-open said valve means whereby to free said housing and said body for gravity-propelled downward travel in said well pipe.

8. A paraflin control device for well pipes, comprising, a generally tubular body insertable in a well pipe for longitudinal movement therein, means carried by the body for controlling paraflin tending to adhere to the wall of said pipe, and means for increasing the effective buoyancy of said body in well fluids present in said pipe com- References Cited UNITED STATES PATENTS 1,993,258 3/1935 Bettis 103-52 2,636,565 4/1953 Williams 166-170 2,674,951 4/1954 Zaba 103-52 3,037,558 6/1962 McGowen et a1. 166-170 3,251,306 5/1966 Plunk 166-170 X CHARLES E. OCONNELL, Primary Examiner. D. H. BROWN, Assistant Examiner. 

8. A PARAFFIN CONTROL DEVICE FOR WELL PIPES, COMPRISING, A GENERALLY TUBULAR BODY INSERTABLE IN A WELL PIPE FOR LONGITUDINAL MOVEMENT THEREIN, MEANS CARRIED BY THE BODY FOR CONTROLLING PARAFFIN TENDING TO ADHERE TO THE WALL OF SAID PIPE, AND MEANS FOR INCREASING THE EFFECTIVE BUOYANCY OF SAID BODY IN WELL FLUIDS PRESENT IN SAID PIPE COMPRISING AN ELONGATE HOLLOW BODY PORTION DEFINING A BUOYANCY CHAMBER, SAID BODY PORTION HAVING LONGITUDINALLY SPACED UPPER AND LOWER OPENINGS THEREIN FOR PASSAGE OF WELL FLUIDS THROUGH SAID CHAMBER, AND MEANS CARRIED BY SAID BODY OPERABLE TO CLOSE AND UPPER OPENINGS WITHOUT CLOSING SAID LOWER OPENINGS WHEN SAID BODY IS AT A LOW POINT IN ITS TRAVEL IN SAID WELL PIPE WHEREBY TO TRAP GASIFORM FLUID EVOLVED IN SAID CHAMBER FROM SAID WELL FLUIDS. 